torre



Oct. 23, 1962 P. TORRE 3,059,625

TWO-STROKE INTERNAL COMBUSTION ENGINE Filed June 8, 1961 s Sheets-Sheet 1 Fig. 7

[b III H I I J V A I I I I I C [P K H J l" r! I; F1 i' K1 J 26 27 F n 8 213 8b :7 a 3 7a 5. 7b

Oct. 23, 1962 P. L. TORRE 3,059,625

TWO-STROKE INTERNAL COMBUSTION ENGINE Filed June 8, 1961 3 Sheets-Sheet 2 Oct. 23, 1962 P. TORRE 3,059,525

TWO-STROKE INTERNAL COMBUSTION ENGINE Filed June 8, 1961 3 Sheets-Sheet 3 United States 3,959,625 Patented Oct. 23, 1962 Free 3,059,625 TWO-STROKE INTERNAL COMBUSTION ENGINE Pier Llllgl Torre, Milan, Italy, assignor of one-half to Innocenti Soc. Gen. per llndustria Metallurgica e Meccanica, Milan, Italy Filed June 8, 1961, Ser. No. 115,762 Claims priority, application Italy June 15, 1960 3 Claims. (Cl. 123-59) This invention relates to two-stroke internal combustion engines of the character including two in-line cylinders and a crankcase which is subdivided by a transverse partition into a pair of pie-compression chambers associated with the respective cylinders through overflow conduits for the mixture, and wherein the latter is drawn from a carburetor into the pre-compression chambers on compression strokes of respective pistons through nonreturn valves opening from a common intake conduit into the respective chambers.

Serious difliculties have been encountered in practice in the attempt of reducing pressure drop across the valves as far as possible thereby to improve the filling factor of the engine. Reed-valves have been employed to this end as non-return valves, having low interia and offering relatively large ports for the flow of fuel mixture to the precompression chambers.

The invention contemplates internal combustion engines of the character specified above, comprising a pair of cylindrical coaxial seatings formed in the said partition on an axis which is transverse to the crankshaft axis and is located between the latter and the bottom of the crankcase and wherein the seatings connect with respective pre-compression chambers and a reed-valve unit is inserted axially into each seating; my co-pending application Ser. No. 115,761, filed June 8, 1961 for Two-Stroke Internal Combustion Engine, shows such an arrangement of parts.

It is an object of this invention to further improve fuel mixture delivery to the pre-compression chambers thereby to further reduce pressure drop across the valves and to assure a wide inflow of the mixture to each of the chambers hence a more uniform and complete filling of the chambers.

Since the chambers are intermittently fed with fuel mixture, surges of pressure necessarily occur in the intake system disturbing more or less the desired operation of the engine depending upon the rotational speed of the latter. A further object of this invention resides therefore in so arranging the non-return valves for the two precompression chambers that surge of pressure due to closure of valves associated with one of the chambers will co-operat-e to open the valves associated with the other chamber.

Further objects and characteristic features of the invention will result from the following description of an embodiment thereof, wherein reference is made to the accompanying drawings in which:

FIGURE 1 is a vertical crosssectional view on line II of FIG. 2 of a two-cylinder two-stroke engine embodying the invention;

FIGURES 2 and 3 are cross-sectional views on lines IIII and IIIIII, respectively, of FIGURE 1.

The engine shown on the drawing comprises an engine block A and a crankcase B having a bottom wall E the crankcase being fluid-tight bolted to the engine block. The latter comprises a pair of in-line cylinder-s C, C with pistons D reciprocable therein. A crankshaft E is rotatable in the chamber enclosed by engine block and crankcase, the crankshaft including a pair of rotationally opposite crank throws F, F for the respective pistons (180 phase shift) and an intermediate journal G between the cranks. The journal G is rotatably supported by a bearing H mounted in a transverse partition formed by mutually complemental wall sections K, K which are castformed with engine block and crank-case, respectively. In this manner each of the cylinders has an underlying precompression chamber associated therewith from which a conventional piston-controlled overflow passage (not shown) extends to the cylinder. A portion of the wall section K (FIG. 1) adjacent the bottom wall of the crankcase is enlarged to thereby enclose a pair of co-axial outwardly opening cylindrical seatings 3, 3, the common axis of which extends transversely of the crankshaft at a location between the latter and bottom wall B of the crankcase.

A reed-valve unit is inserted axially into each seating in a direction from the respective lateral side of the crankcase. The valve units are similar to each other and com prise each a valve body M, N (FIG. 2) respectively, which comprises an intermediate flattened section extending between a pair of cylindrical end flanges. Each of the valve bodies can be imagined as a cylindrical block, a longitudinally intermediate section of which has been planed on diametrically opposite sides, whereby the said section (denoted by 21 on FIG. 2) exhibits a pair of diametrically opposite flats and ends by cylindrical flanges 22, 23. A recess 5 axially extending through the body from the axially inner flange 22 into the proximity of the axially outer flange 23 is formed in each valve body, and the flats on the body are crossed by valve ports 7a, 7]), respectively, controlled by reeds 8a, 8b, respectively. The recesses 5 in the two valve bodies centrally connect with a common suction conduit 6 (FIG. 3) extending through the crankcase bottom B into the partition Wall section K radially of the intermediate bearing H.

The valve bodies each seal against their respective cylindrical seats 3 by cylindrical end flanges 22, 23 and by the two diametrically opposite cylindrically curved surfaces connecting the flats (FIG. 1). In order to improve sealing circumferential grooves 22a are formed in the axially inner flanges 22, and the cylindrically curved surface portions are formed with grooves 21a extending parallel with generatrices, the axially outer flanges 23 being formed each with an outer bead 23a acting as a cover and cooperating with a flat annular seal 24 ('FIG. 3) compressed against the crankcase.

The valve bodies are so angularly orientated in their seats (compare FIG. 1) that the flattened intermediate section 21 on each body is co-planar with the partition K, K and the free ends of the reeds 8a, 8b are directed towards the crankshaft. In this manner, each seating 3 is subdivided into a pair of diametrically opposite cavities which are sealed with respect of each other by the section 21. The reed-valve set 8a in each valve unit directly opens into a passage 26 in wall section K connecting with the pre-compression chamber associated with the cylinder C, and reed-valve set 8b in each unit directly opens into a passage 27 connecting with the pre-compression chamber associated with the cylinder C Each of the two valve units M, N controls both pro-compression chambers in the crankcase.

Since induction in the two cylinders is effected in phase shift the left hand reed-valves 8a and the right hand reedvalves 8b on FIGURES 1 and 2 will alternately open and close in phase, whereby surge of pressure in recesses 5 due to closure of valves 8a, for example, will co-operate in opening valves 8b and vice-versa, without a substantial back-propagation from one recess 5 to another and to induction conduit 6.

It will be also seen that the passages 26, 27 are appreci-ably elongated (FIG. 2) transversely of the crankshaft whereby large courtain-like flows of fuel mixture are :3 induced into the respective pre-compression chambers thereby to thoroughly fill the chambers on each induction process.

What I claim is:

l. A two-stroke internal combustion engine comprising an engine block having a pair of in-line cylinders therein, a crankcase having a bottom wall, the said engine block and crankcase jointly enclosing a chamber, a crankshaft rotatable in the chamber including a pair of cranks and an intermediate journal, a transverse partition in the said chamber extending between the pair of cranks subdividing the chamber into a pair of pre-compression chambers as sociated with the respective cylinders, a pair of cylindrical axially aligned seatings formed in the partition on an axis which is transverse to the longitudinal axis of the crankshaft and is located between the said intermediate journal and bottom wall of the crankcase, a pair of nonreturn reed-valve units axially inserted into respective seatings each of which includes a valve body comprising a pair of cylindrical opposite end flanges engaging in opposite end portions of the respective seating and a flattened intermediate section between the flanges in an arrangement co-planar with the said partition thereby subdividing the seating into a pair of diametrically opposite cavities, each of the seatings having associated therewith a pair of passages formed in the crankcase connecting the respective cavities with the respective pre-compression chambers, a recess extending into the intermediate section of each of the valve bodies through axially inner flange of the body, reed-controlled apertures in the said intermediate section of the body providing an intake-connection between the respective diametrically opposite cavities and the recess in the valve body, and an intake passage through the bottom wall of the crankcase connecting with the recesses in the two valve bodies.

2. In the internal combustion engine as claimed in claim 1, the said passages in the crankcase of a cross sectional shape elongated transversely of the crankshaft thereby to provide large courtain-like flow of fuel mixture into the respective pie-compression chambers.

3. In the internal combustion engine as claimed in claim 1, the reeds on the said valve bodies having their free ends turned towards the respective passages in the crankcase.

References Cited in the file of this patent UNITED STATES PATENTS 2,973,752 Torre Mar. 7, 1961 

